Water damage to books, papers, and other similar material has been a problem for as long as there have been collections of books and documents. Traditional book drying methods have tended to primarily focus either on the use of centralized, high technology equipment, or on labor-intensive manual methods (or combinations of both). Unfortunately, books and other similar material are not unlike sponges. Because paper is hydroscopic, a bound book can absorb up to 200% of its original weight in water. The addition of such large amounts of water can lead to swelling or expansion of the book/paper. The text-block of a soaked book typically expands against its binding, causing the spine of the book to become concave in shape, and forcing the text-block to become detached from the binding. In fact, the majority of water damage to bound books is caused by such swelling and typically takes place within the first four hours after exposure of the material to water. The board cores of bindings can also absorb a great amount of water and are usually the source of mold development between the board papers and fly leaves. Wet books and papers are subject to mechanical, chemical, and cosmetic damage within hours of becoming damp.
Throughout its history, the field of library preservation has responded to major disasters by creating new recovery technology. For example, in 1966 , floods in Florence, Italy inundated millions of books and manuscripts. In response to the flood, the use of commercial food freeze-drying technology to remove moisture from books was pioneered to assist in handling the enormous quantity of material that was damaged.
Major disasters such as the 9/11 terrorist attacks on the United States (which caused substantial damage to the Pentagon Library, the 2002 Central European floods (which inundated about 50 Czech Republic libraries containing more than 600,000 volumes), and hurricanes such 2005's Katrina, continue to highlight the need for fast, portable, and inexpensive recovery/conservation techniques for books and paper materials. Again, such disasters have driven new technology development through renewed awareness, yet each presents novel challenges, e.g., damage to old printed books with leather bindings, unique historical drawings and architectural plans, photographs, music manuscripts, etc.
Various previous methods for drying are outlined briefly below. It will be noted that not many methods exist, despite the number and extent of disasters and the value of the materials involved. To further complicate matters, such traditional methods do not work well for all situations and there are numerous instances where the traditional methods are not feasible or appropriate.
Literature produced by the Northeast Document Conservation Center (NEDCC), Emergency Salvage of Wet Books and Records, Emergency Management, Section 3 , Leaflet 7, 1999 , outlines various procedures for drying materials such as books, e.g., air drying, freezer drying, cryogenic drying, vacuum freeze drying, and vacuum thermal drying. Other traditional methods for drying wet documents, include vacuum bags (containing the material to be dried) that are transferred to a freeze drying chamber, heated press devices for organic materials, heated vacuum chambers, and freezing and maintaining materials below freezing. The general literature reveals that vacuum drying and vacuum freeze-drying are typically the most common methods for drying wet materials. Other drying processes include warm air (e.g., used to dry deacidified paper), and vacuum pressure used in conjunction with high frequency radiation.
Air-drying is the oldest method for drying books and paper. It is labor and time intensive, sometimes taking days to weeks to dry a book. Since paper will give off water if exposed to air, wet books can be stood up and fanned out allowing them to lose a large quantity of moisture to the air. Fans may also be employed to assist in evaporation. In any event, however, drying can take days to occur, and there is the potential of cockling or wrinkling of the paper in the text-block. Subsequent work requires that the drying books be interleaved with blotter and restrained under pressure. The expansion of the wet books can require 20-to-30 percent more shelf space because of swelling, etc. In general, air-drying is most suitable for small numbers of damp or slightly wet books and documents.
Freeze-drying using a self-defrosting blast freezer and Forced-air drying under pressure and vacuum packing are other methods of drying books, papers, etc. However, such methods also have a number of drawbacks, e.g., expense, length of time required, etc.
In addition to drying books, papers, and other objects, it is also often desirable to humidify them, e.g., in order to relax brittle pages or to prevent shrinkage and warpage, etc.
A welcome addition to the art would be methods and devices to quickly and conveniently dry and humidify books, paper, records, film, photographs, and similar materials, as well as other objects, even in large quantities at a low cost and without the need for off-site shipment and expensive or complex equipment. The present invention provides these and other benefits that will be apparent upon examination of the following.